1. Field of the Invention
The present invention relates to an image processing technology in a graphics processor or the like.
2. Description of the Related Art
With the remarkable development of computer graphics technology and image processing technology used in computer gaming, digital broadcast etc, in recent years, more detailed display of three-dimensional graphics etc. has become possible. In three-dimensional graphics processing, a three-dimensional object having three-dimensional coordinate data is projected onto a two-dimensional screen for display on a display or the like.
Normally, a three-dimensional object is modeled using a combination of polygons (e.g., triangles). In projecting a three-dimensional object onto a two-dimensional screen, rasterization is performed wherein values like luminance of pixels inside the polygons are calculated by referring to data on vertices of the polygons.
In rasterization, a linear interpolation method called Digital Differential Analyzer (DDA) is used. DDA allows obtaining gradient between data for a vertex of a polygon and data for another vertex of the polygon in the direction of a side of the polygon. The gradient thus obtained is used to compute data for the polygon sides. Subsequently, pixels inside the polygons are generated by computing the gradient in the raster-scan direction.
Patent document 1 discloses a technology for improving rendering speed whereby a pixel group comprising a plurality of pixels included in a predefined rectangular area is dealt with as a unit of processing and a set of pixel groups are transmitted to a processing block in the subsequent stage.
Patent document 2 teaches an improvement over the technology described in patent document 1. Processing efficiency is improved by merging multiple pixel groups into a single pixel group before transmitting the same to a processing block in the subsequent stage.
[patent document 1]JP 2000-338959 A
[patent document 2]JP 2003-123082 A
With improvements in the performance of image processing apparatuses for processing three-dimensional computer graphics in recent years, the size of a polygon forming a three-dimensional object tends to be smaller in order to render a more detailed three-dimensional object. Consequently, pixel groups including only a limited number of valid pixels are increasingly more likely to be generated. In this background, more efficient merge of rectangular areas (pixel groups) is called for.